we're adopting several promotional techniques which we're engineering into our product at yeblogger.com. This includes widgets and toolbars. the point is to help users promote your product to other users simply by using it, also - retention is important. the effectiveness of any marking technique disappears if you can't retain your customers.
now, more importantly. do you want to promote your site? send me a pm and I will build you a blogging community like yeblogger.com. within 90 days, I'll guarantee you that every significant blogger relevant to your industry will be on your mailing list, so you can promote your site to people who can promote it to other people (through their blogs) until the cows come home.
i think this would be a much better investment in marketing rather than
SEO, or straight advertising. with a blog community - you have residual value. ie, the money you spend on your community can be recovered when you sell your community.
this is not the case with ads; once you spend the money - you never see it return